What is the maximum resistance to ground for a grounding electrode system according to NEC?

The National Electrical Code (NEC) stipulates that the maximum resistance to ground for a grounding electrode system should not exceed 25 ohms. This requirement is established to ensure effective grounding and bonding, which are critical for safety in electrical installations. A grounding system with a resistance of 25 ohms or less helps mitigate the risk of electric shock and improves the performance of overcurrent protective devices by providing a low-resistance path for fault currents.

Ground resistance higher than this threshold may not effectively control voltages during a fault condition, potentially leading to hazardous situations. Therefore, maintaining a grounding resistance of 25 ohms or lower is essential for proper electrical protection and system operation.